A first-trimester screening test can reliably identify fetuses likely to be born with Down syndrome, providing expectant women with that information much earlier in a pregnancy than current testing allows, according to a major study being released today.

The eagerly awaited study of more than 38,000 U.S. women -- the largest ever conducted -- found that the screening method, which combines a blood test with an ultrasound exam, can pinpoint many fetuses with the common genetic disorder 11 weeks after conception. That allows women to decide sooner whether to undergo the riskier follow-up testing needed to confirm the diagnosis.